1. Field of the Invention
The present invention relates to stage apparatuses for positioning an object mounted thereon, and more particularly, though not exclusively, to stage apparatuses which can be used as reticle stages for exposure apparatuses.
2. Description of the Related Art
Stage apparatuses are used in exposure apparatuses to position a substrate or an original (hereinafter collectively referred to as a substrate). Japanese Patent Laid-Open No. 2004-079639 discusses a stage apparatus that utilizes the repulsive force of permanent magnets to accelerate or decelerate a stage holding a substrate.
The stage apparatus discussed in Japanese Patent Laid-Open No. 2004-079639 will be described with reference to FIGS. 12A and 12B. A stage 104 holding a substrate 103 is movable along a guide 102 in the Y direction. The stage 104 has linear motor sliders 105 and is driven in the Y direction by a force generated between the linear motor sliders 105 and linear motor stators 106 attached to a base (not shown).
The stage 104 has a pair of permanent magnets 109 in the front and rear thereof in the direction in which the stage 104 is moved. The guide 102 has two pairs of upper and lower permanent magnets 112 separated by a predetermined distance. The permanent magnets 109 and 112 are magnetized in the Z direction so that opposing surfaces thereof have the same pole. When the permanent magnets 109 are inserted between the permanent magnets 112 at either end of the stroke of the stage 104, a repulsive force is generated therebetween to accelerate or decelerate the stage 104.
The stage 104 causes a drive reaction force when driven by the repulsive force of the permanent magnets 109 and 112. The drive reaction force vibrates the entire apparatus. Such vibration disturbs the positioning control of the stage 104, thus contributing to decreased positioning accuracy or extended positioning time.